1. Field of the Invention
The present invention relates to an image capturing apparatus and a control method therefor, and more particularly, to a technique for displaying the degree of in-focus in an image capturing apparatus.
2. Description of the Related Art
In conjunction with advances in automatic focus detection (AF) techniques, AF is mainly used for focus detection in image capturing apparatuses such as still cameras and video cameras. However, under conditions in which focusing through AF is hard to carry out, such as in a case in which strict focusing is required as in macro image capturing, or in a case in which defocused images are intentionally captured, images are often captured through manual focus adjustment (MF).
In particular, in a case in which MF operation is to be carried out, operability and accuracy in focusing are greatly affected by the resolution of an optical finder or an electronic viewfinder (EVF). However, increases in optical finders and display devices in terms of size and resolution leads to increases in image capturing apparatuses in terms of size and price. Therefore, at present it is difficult to say that every image capturing apparatuses is equipped with an optical finder or a display device sufficient to achieve easy and high-accuracy MF operation.
Thus, in order for photographers to figure out the degree of in-focus (in-focus state) more clearly, various assist indications have been introduced, including, for example, highlighting (peaking) for focused edge portions of a captured image and partially enlarged indications for checking the in-focus state.
Furthermore, Japanese Patent Laid-Open No. 6-121184 discloses a method of obtaining the integrated value for high-frequency components of luminance signals from an image as an “evaluation value” indicating the degree of in-focus, and synthesizing and displaying, in the form of a bar graph, changes in magnitude of the integrated value onto an EVF image.
Moreover, Japanese Patent No. 4089675 discloses a method of generating a histogram of the magnitude of a high-frequency component for captured image signals as an “evaluation value” indicating the degree of in-focus, and synthesizing and displaying the histogram onto an EVF image.
While peaking refers to highlighting of focused edge portions of an EVF image, it is hard to distinguish the highlighting depending on the sizes and locations of the focused edge portions. Furthermore, there has been an attempt to color only focused edge portions of an EVF image, whereas the rest of the image is displayed in black and white. However, this approach has a problem in that the change to the display in black and white degrades the visibility of the captured object through the EVF.
In addition, in the methods disclosed in Japanese Patent Laid-Open No. 6-121184 and Japanese Patent No. 4089675, it is difficult to figure out which part has the degree of in-focus indicated by the “evaluation value” indicating the degree of in-focus. Furthermore, since the change in the magnitude of the integrated value is expressed by the height of the bar graph or the spread of the histogram, it is not easy to figure out the maximum value of the evaluation value.